Effect of non-thermal plasma exposure on regrowth potential of foodborne and nosocomial pathogens

Summary form only given. The effective sterilization of foodborne and opportunistic nosocomial pathogens is a major problem in food industry, biomedical and hospital applications, respectively. We present the results of indirect exposure of a portable plasma source as a non-thermal sterilization method and its effects on regrowth potential of post-partial-plasma-exposure of foodborne and nosocomial pathogens [1]. We have investigated the plasma efficiency at different bacterial concentrations for its effects on growth for pre and post plasma treated bacteria. The cold plasma was applied to Escherichia coli ATCC 11775, Bacillus cereus ATCC 14579, Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853. An average of 30 CFU per 71 mm² was inoculated with the corresponding bacterium on a dry surface-agar plate, followed by the following exposure times 0, 30, 60,120 and 180 seconds of plasma. 20 μl of E. coli 10⁷ CFU/ml and P. aeruginosa 10⁸ CFU/ml were treated with plasma for 0, 120, 240 and 360 seconds. The colonies that survived the plasma treatment and control colonies were transferred to tryptic soy broth (TSB) and their growth was observed for 24 hrs. Results have showed 100 % and 96% of inactivation after 180s of treatment for E. coli and S. aureus respectively. A 100% of inactivation was observed for B. cereus and P. aeruginosa after 60s. E. coli and P. aeruginosa showed a log reduction of 3.4 and 3.9 orders respectively after 360s. The growths of survived colonies were monitored and subjected to further treatment. From the measurements we have estimated the “plasma treatment regime” based on the most effective exposure time and the status of the microbial colonization, and the results will be presented. The cold plasma is effective in sterilizing bacteria at different concentrations with potential applications in the food industry and the medical field.